The invention provides nucleotide sequences from coryneform bacteria which code for the citB gene and a process for the fermentative preparation of amino acids, in particular L-lysine, by attenuation of the citrate utilization gene B (citB gene). The citB gene codes for the CitB protein, which is a transcription regulator of a two-component system. All references cited herein are expressly incorporated by reference. Incorporation by reference is also designated by the term “I.B.R.” following any citation.
L-Amino acids, in particular L-lysine, are used in human medicine and in the pharmaceuticals industry, in the foodstuffs industry and very particularly in animal nutrition.
It is known that amino acids are prepared by fermentation from strains of coryneform bacteria, in particular Corynebacterium glutamicum. Because of their great importance, work is constantly being undertaken to improve the preparation processes.
Improvements to the process can relate to fermentation measures, such as, for example, stirring and supply of oxygen, or the composition of the nutrient media, such as, for example, the sugar concentration during the fermentation, or the working up to the product form by, for example, ion exchange chromatography, or the intrinsic output properties of the microorganism itself.
Methods of mutagenesis, selection and mutant selection are used to improve the output properties of these microorganisms. Strains which are resistant to antimetabolites or are auxotrophic for metabolites of regulatory importance and which produce amino acids are obtained in this manner.
Methods of the recombinant DNA technique have also been employed for some years for improving the strain of Corynebacterium strains which produce L-amino acids.
The invention provides new measures for improved fermentative preparation of amino acids, in particular L-lysine.